GMAT Critical Reasoning (CR) | Re: In a certain population, the two most heavily diagnosed

In a certain population, the two most heavily diagnosed diseases are schistosomiasis and malaria.
Over the past five years, malaria has accounted for more than half of all disease cases, and
schistosomiasis, which accounted for 40% of all disease cases in the community five years ago, accounted for 30% in the past year.

Notice the pattern of data given. Data regarding malaria is given over a time whereas data at two times is given for Schisto.....

Which of the following must be true on the
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